ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P71. Interaction of Ruthenium and Gold Derivatives of H2TMPyP 4+
(Ru(II)TMPyP 4+ and Au(III)TMPyP 5+ ) with DNA
M.D. A. Habib a , M. Tabata b
a
Department of Chemistry, University of Dhaka, Dhaka, 1000, Dhaka, Bangladesh
e-mail: mahabibbit@yahoo.com
b
Chemistry, Saga University, Saga, Saga, Japan
We investigated the interaction of free base porphyrin, tetrakis(1-methylpyridium-4-yl)porphyrin (H2TMPyP 4+ ),
and its metallo-derivatives of ruthenium(II) and gold(III) with DNA using UV-vis, fluorescence and circular
dichroism (CD) spectroscopy at 0.1 M NaCl, 7.5 pH and 25 °C. The results indicated that Ru(II)TMPyP 4+
interacted with DNA via outside binding with self-stacking manner. This is because the UV-vis data indicated
that a small red shift (∆λ = 3 nm) and a minimal hypochromicity (10%) were observed upon addition of DNA.
Moreover, the CD spectra of DNA indicated that a new peak was developed at the Soret region upon the addition
of the Ru(II)TMPyP 4+ . However, in the case of Au(III)TMPyP 5+ , a significant hypochromicity (55%) was
observed at high concentration (5.0x10-4 M bp) of DNA but a small red shift (∆λ = 4.5 nm) was observed.
Moreover, the CD results indicated the development of positive and negative peaks at the Soret region during the
titration of DNA with Au(III)porphyrin. Therefore, both the spectroscopy results indicated that Au(III)TMPyP 5+
interacted with DNA as outside binding with a partial intercalation. On the other hand, the free base porphyrin,
H2TMPyP 4+ , interacted with DNA as intercalation because the UV-vis results indicated a significant
hypochromicity (30%) and a large red shift (∆λ = 20 nm). In addition, the CD results also indicated only a
negative peak was developed at the Soret region during the titration of DNA with the free base porphyrin.
Fluorescence spectroscopy results indicated that initially the aggregated porphyrins de-aggregate and then
interacted with DNA upon addition of DNA. This phenomenon has been confirmed with the fluorescence
experiments of the porphyrins in the presence of different concentrations of NaCl and ethanol.
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